State recovery methods and apparatus for computing platforms

ABSTRACT

State recovery methods and apparatus for computing platforms are disclosed. An example method includes inserting a first instruction into optimized code to cause a first portion of a register in a first state to be saved to memory before execution of a region of the optimized code; and maintaining a value indicative of a manner in which a second portion of the register in the first state is to be restored in connection with a state recovery from the optimized code.

FIELD OF THE DISCLOSURE

This disclosure relates generally to computing platforms and, moreparticularly, to state recovery methods and apparatus for computingplatforms.

BACKGROUND

Some computing platforms attempt to improve machine level execution ofcode by translating the code according to one or more optimizationtechniques. For example, original code corresponding to an iterativeloop may be optimized into translated code to better utilize resourcesof the computing platform. In such instances, when the translated codeis executed in lieu of the original code, an event (e.g., an interrupt,an exception, a trap, termination of an iterative loop, etc.) may resultin a need to recover a state of the computing platform. For example,when an interrupt occurs during execution of translated codecorresponding to an iterative loop, the system may need to recover to astate that would have resulted from execution of the original code. Thestate of the computing platform to be recovered includes informationsuch as, for example, register content and/or pointer values (e.g., avalue of a program counter corresponding to an instruction of theoriginal code). As the translated code often includes differentinstructions and/or differently ordered instructions than the originalcode, recovery of the state of the computing platform presentschallenges.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a block diagram of an example computing platform including anexample state recovery mechanism disclosed herein.

FIG. 2 is a representation of an example loop in original code.

FIG. 3 is a representation of the example loop of FIG. 2 in translatedcode that utilizes the example return instruction pointer (RIP) recoveryregister of FIG. 1.

FIG. 4 is a representation of the example loop of FIG. 2 in translatedcode that utilizes the example RIP recovery table of FIG. 1.

FIGS. 5-7 are flowcharts representative of example machine readableinstructions that may be executed to implement the example staterecovery mechanism of FIG. 1.

FIG. 8 is a block diagram of an example processing system capable ofexecuting the example machine readable instructions of FIGS. 5-7 toimplement the example state recovery mechanism of FIG. 1.

DETAILED DESCRIPTION

Example methods, apparatus, and articles of manufacture disclosed hereinprovide a state recovery mechanism for computing platforms that optimizeoriginal code into translated code. In particular, examples disclosedherein enable such computing platforms to recover to an expected state(e.g., according to execution of the original code) when, for example,an exit from an execution of the translated code occurs (e.g., inresponse to an interrupt, exception, trap, etc.) or when an iteration ofthe translated code ends. The state of the computing platform to berecovered includes information such as, for example, register contentand/or pointer values (e.g., a value of a program counter correspondingto an instruction of the original code) corresponding to a point inprogram execution to which the computing platform is to return.

As described in greater detail below, examples disclosed herein insertinstructions and/or metadata into dynamically translated code thatenable recovery of register values and/or pointer values. Moreover, asdescribed in greater detail below, examples disclosed herein interpretinformation provided by a generator of the translated code (e.g., anoptimizer operating according to one or more optimization techniques totranslate the code). Examples disclosed herein utilize theinterpretations to generate and maintain one or more tracking values(e.g., bitvectors) that indicate how the state of the registers is to berecovered should the need arise.

Examples disclosed herein utilize the inserted instructions and thetracking values to recover the proper state of the computing platformwhen needed. In doing so, examples disclosed herein avoid the need torepeatedly move (e.g., copy) data of the registers and/or pointers foreach region (e.g., atomic region) of the translated code and/or for eachiteration of the translated code. Moreover, the significant additionaloverhead incurred by having to repeatedly move the data is avoided viathe examples disclosed herein.

FIG. 1 illustrates an example computing platform 100 in which examplemethod, apparatus, and/or articles of manufacture disclosed herein canbe implemented. FIG. 1 includes a code optimizer 102 that the computingplatform 100 uses to improve performance through one or moreoptimization techniques. In particular, the example code optimizer 102includes a translator 104 that receives a set of original instructionsand alters the original code to form translated code. As used herein,the terms “original code” and “original instructions” refer topre-optimization code or instructions of, for example, a program orapplication. For example, the term “original instructions” may refer tonative and/or non-native instructions that have not yet been or whichwill not be translated by the code optimizer 102 and/or any otheroptimization component. As used herein, the terms “translated code” and“translated instructions” refer to post-optimization code orinstructions code of, for example, a program or application. Forexample, “translated instructions” may refer to instructions that havebeen translated by the translator 104 of the code optimizer 102 and/orany other optimization component.

In the illustrated example of FIG. 1, the translator 104 implements avector widening technique to optimize original code. Vector wideningoptimization is useful when original code intended for execution viaregisters of a first size is to be executed via registers of a secondsize larger than the first size. In other words, original code may beintended for compilation and execution on a first machine havingregisters of the first size. However, the original code may be compiledand executed on a second machine (e.g., a more modem or advancedcomputing platform than the first machine) having registers of thesecond, larger size. In such instances, vector widening optimizationtranslates the original code to take advantage of the additional spacein the larger registers of the second machine.

In some examples, vector widening optimization involves using theadditional bits (e.g., relative to the amount of register bits expectedby the original code) of the larger registers for parallel execution ofmore than one instruction (or set of instructions) in the same register.For example, the translator 104 may generate optimized code that enablesmultiple threads (e.g., each corresponding to adjacent loop iterations)to utilize the same register by, for example, using the upper bits ofthe larger registers. Without the vector widening optimization providedby the example translator 104, the multiple threads utilize separateregisters. Accordingly, the vector widening optimization provided by theexample translator 104 results in more efficient use of system resourcesand, thus, better performance (e.g., as measured by processing speed).The vector widening optimization implemented by the example translator104 of FIG. 1 is further described below in connection with FIGS. 2-4.

The example translator 104 of FIG. 1 also utilizes restrictedtransactional memory (RTM) in connection with the optimization of theoriginal code. In brief, RTM provides a hardware mechanism for executingcode in atomic regions, which may be executed in parallel. An atomicregion of code (sometimes referred to as a transaction) is an isolatedset of instructions that writes to registers and memory as theinstructions are executed. The register and memory writes of an atomicregion are committed when the region is fully executed (e.g., eachinstruction of the region is executed as intended). However, whenexecution of the atomic region is aborted (e.g., in response to aninterrupt), the writes made during execution of the atomic region arerolled back or undone. RTM and the associated instructions enablehardware to implement the rollback of the register and memory writes.When RTM is used to execute code, some instructions are grouped into anatomic region or transaction that is defined by an RTM_BEGIN instruction(e.g., XBEGIN in an Intel® architecture) and an RTM_END instruction(e.g., XEND in an Intel® architecture).

To enable the rollback of register and memory writes made during atransaction, systems in which RTM is implemented provide data to othersystem components (e.g., state recovery components) depending on, forexample, a point in the code at which an abort event (e.g., aninterrupt, a trap, an exception, etc.) occurs. If an abort event occurswhen code within a defined RTM transaction or region (e.g., between thecorresponding RTM_BEGIN and RTM_END instructions) is being executed, anaddress of the corresponding RTM_BEGIN instruction is made available to,for example, state recovery components. If an abort event occurs whencode outside a defined RTM transaction or region (e.g., outside thecorresponding RTM_BEGIN and RTM_END instructions) is being executed, aprogram counter (e.g., a pointer an address) of the last retiredinstruction in the translated code is made available to, for example,state recovery.

Thus, the example optimizer 102 and the example translator 104 of FIG. 1implement a vector widening optimization for instructions to be executedin RTM. The vector widening optimization improves performance oforiginal code via utilization of additional register space. Further, theuse of RTM enables transactional execution of code that can be rolledback such that the computing platform 100 can recover to a particularstate. While the examples disclosed herein are described in connectionwith vector widening and RTM, the examples disclosed herein can beutilized in additional or alternative environments and/or in connectionwith additional or alternative types of optimizations.

The example of FIG. 1 includes a state recovery mechanism 106constructed in accordance with teachings of this disclosure. Asdescribed in greater detail below, the example state recovery mechanism106 of FIG. 1 inserts instructions disclosed herein into translated oroptimized code to enable a recovery of a state of the computing platform100. Moreover, as described in detail below, the example state recoverymechanism 106 of FIG. 1 generates and maintains tracking values (e.g.,bitvectors) that store information that can be used to recover a stateof the computing platform 100. In other words, the example trackingvalues generated and maintained by the example state recovery mechanism106 of FIG. 1 indicate a manner in which the state of the computingplatform 100 can be recovered. To generate and maintain such trackingvalues, the state recovery mechanism 106 of FIG. 1 communicates with ametadata interface 108 of the example optimizer 102. As described indetail below, the example optimizer 102 provides information related tothe translation of original code to the state recovery mechanism 106 viathe metadata interface 108. In some examples, the metadata interface 108facilitates the communication between the state recovery mechanism 106and the optimizer 102 via a handshake relationship. For example, themetadata interface 108 informs the example state recovery mechanism 106of locations (e.g., within registers and/or in memory) at which datacorresponding to the recovery state can be retrieved. Additionalcommunications between the example state recovery mechanism 106 and themetadata interface 108 are described below.

The example state recovery mechanism 106 of FIG. 1 includes a statepreserver 110 and a state restorer 112. The example state preserver 110of FIG. 1 provides instructions and tracking values that enable thestate restorer 112 to recover the computing platform 100 to a desiredstate in response to, for example, an exit event (e.g., an abort, atrap, an exception) or completion of an atomic region of the translatedcode. For example, when translated code experiences an exit event or aregion of the translated code has been completed, the return instructionpointer (RIP) of the translated code points to an address of thetranslated code to which execution is to jump in response to the eventor completion. To properly recover the desired state of the computingplatform 100 when needed, the example state preserver 110 tracks anaddress of the original code associated with the address of thetranslated code to which the RIP points. In other words, the RIP of thetranslated code points to a point in the translated code and the statepreserver 110 tracks (and makes available to the example state restorer112) the address in the original code corresponding to that point in thetranslated code. By tracking the address in the original codecorresponding to the RIP of the translated code, the example statepreserver 110 is aware of the address in the original code to whichexecution should return upon, for example, completion of the translatedcode or an exit from the translated code. The address of the originalcode at which execution resumes (e.g., when exiting from a loop beingexecuted via translated code) is sometimes referred to as a programcounter (PC). In other words, the PC for the original code correspondsto an address of the next instruction of the original code to beexecuted.

The example state preserver 110 of FIG. 1 includes first and secondmechanisms to track and recover the appropriate PC for the originalcode. In particular, the example state preserver 110 of FIG. 1implements a PC recovery register 114 and a PC recovery table 116. Theexample PC recovery register 114 stores an address of the original codefor the PC in the native format of the original code addressing scheme.The example state preserver 110 cooperates with the example optimizer102 to insert load instructions into the translated code that load theappropriate address (e.g., the original code address for the appropriatenext instruction) into the PC recovery register 114. The loadinstructions for the PC recovery register 114 are inserted into thetranslated code at points in execution at which the value of the PCshould be updated. For example, when an exit event occurs in connectionwith the translated code during execution of an atomic region (e.g., achunk of code corresponding to an iteration of a loop), the value of thePC to be loaded into the PC recovery register 114 should be a firstvalue. Further, when an exit event occurs in connection with thetranslated code after execution of the atomic region is complete, thevalue of the PC to be loaded into the PC recovery register 114 should bea second value different than the first value. In this example scenario,the example state preserver 110 cooperates with the code optimizer 102to insert a first load instruction for the PC recovery register 114 at afirst point in the translated code before the atomic region. The firstload instruction moves the first value for the PC into the PC recoveryregister 114. Further, the example state preserver 110 cooperates withthe code optimizer 102 to insert a second load instruction for the PCrecovery register 114 at a second point in the translated code after theatomic region. The second load instruction moves the second value forthe PC into the PC recovery register 114. Accordingly, the example PCrecovery register 114 of FIG. 1 stores a value corresponding to theaddress in the original code depending on a location in the translatedcode at which the exit event occurs.

An example implementation of the recovery ability provided by the PCrecovery register 114 is shown in connection with FIG. 2 and FIG. 3.FIG. 2 illustrates an example section of original code 200 that is to betranslated by the example translator 104. The example original code 200of FIG. 2 is a SAXPY loop (Single-precision alpha X plus Y). The exampleof FIG. 2 shows an address for each instruction of the original code200. FIG. 3 illustrates an example translation 300 of the original code200 of FIG. 2. The example translated code 300 of FIG. 3 includesdifferent instructions than the original code 200 and, thus, presentschallenges to recovering the proper PC and the proper state of thecorresponding registers. As described above, the example computingplatform 100 includes restricted transactional memory (RTM) and theexample translator 104 optimizes the original code 200 accordingly. Forexample, as shown in FIG. 3, the SAXPY loop of the original code 200 hasbeen placed into an RTM transaction by the translator 104. The RTMtransactions (which are atomic regions in the example of FIG. 3) arerespectively defined by an RTM_BEGIN instruction and an RTM_ENDinstruction. For example, several instructions of the SAXPY loop areimplemented in an atomic region 302 of the translated code defined by afirst RTM_BEGIN instruction and an RTM_END instruction.

Reference to FIG. 2 shows that an exit event occurring within the atomicregion 302 of the translated code 300 should correspond with a return toaddress 0x40490a of the original code 200. As described above, an exitevent occurring within an RTM transaction causes the RIP of thetranslated code to point to the beginning of the transaction (e.g., thecorresponding RTM_BEGIN instruction). Therefore, when an exit eventoccurs within the atomic region 302 of FIG. 3, the address of theoriginal code to which the PC should correspond is the beginning of theloop. Accordingly, the example state preserver 110 of FIG. 1 cooperateswith the code optimizer 102 to insert a first load instruction (movRR=0x40490a) into the translated code 300 before the atomic region 302to load the address of the beginning of the loop in the original code200. As a result, the PC recovery register 114 will store a value of0x40490a during execution of the atomic region 302. Moreover, theexample state preserver 110 of FIG. 1 cooperates with the code optimizer102 to insert a second load instruction (mov RR=0x404938) into thetranslated code 300 before a second atomic region 304 to load adifferent address of the original code 200. In particular, the PCrecovery register 114 is loaded with a value of 0x404938 duringexecution of the second atomic region 304. As shown in FIG. 2, thisaddress in the original code 200 corresponds to a loop instruction.Moreover, the example state preserver 110 of FIG. 1 cooperates with thecode optimizer 102 to insert a third load instruction (mov RR=0x40493a)into the translated code 300 after the first and second atomic regions302, 304 to load a different address of the original code 200. Inparticular, the PC recovery register 114 is loaded with a value of0x40493a after execution of the first and second atomic regions 302,304. As shown in FIG. 2, this address in the original code 200corresponds to a next instruction in the original code 200.

Thus, the example state preserver 110 of FIG. 1 maintains the value ofthe example PC recovery register 114 (e.g., via one or more loadinstructions) to correspond to the appropriate address of the originalcode 200 to which execution is to return. In some examples, the statepreserver 110 uses data provided by the optimizer 102 via the metadatainterface 108 to determine which address of the original code 200corresponds to the RIP of the translated code 300 during execution ofthe translated code 300 and/or as the original code 200 is optimized. Inother words, the example optimizer 102 can inform the example statepreserver 110 of the appropriate address of the original code 200 thatshould be loaded into the PC recovery register 114 depending on, forexample, a value of the RIP for the translated code at different pointsin the translated code 300.

Alternatively, the example state preserver 110 of FIG. 1 can utilize theexample PC recovery table 116 to track the correct value of the PC forthe original code at different points within the translated code.Similar to the use of the PC recovery register 114 described above, theexample state preserver 110 of FIG. 1 utilizes data from the optimizer102 regarding a correspondence between the current RIP of the translatedcode and the proper address for the PC of the original code. In otherwords, the example state preserver 110 communicates with the metadatainterface 108 of the code optimizer 102 to determine which value of thePC is appropriate at different point in execution of the translatedcode. Instead of inserting load instructions into the translated code asdescribed above in connection with the example PC recovery register 114,the example PC recovery table 116 includes one or more address ranges inthe translated code and the corresponding appropriate value of the PC ofthe original code.

FIG. 4 illustrates an example implementation of the example PC recoverytable 116 of FIG. 1. In particular, FIG. 4 includes translated code 400generated by the example translator 104 based on the original code 200of FIG. 2 (e.g., the SAXPY loop code). The example translated code 400is logically similar to the translated code 300 of FIG. 3, but does notinclude the load instructions associated with the PC recovery register112 of FIG. 1. The example translated code 400 of FIG. 4 includesmultiple boundaries (e.g., atomic region boundaries) that eachcorrespond to a beginning of one address range and an end of anotheraddress range. The example table 116 of FIG. 4 includes address rangeentries 402 for the translated code 400. At some of the boundaries(e.g., transitions between address ranges 402), the appropriate PC valuefor the original code (e.g., an address in the original code to whichexecution should jump in the event of an exit from the translated code)undergoes an update or change. Thus, while a first one of the addressranges has a first PC value for the original code, a second one of theaddress ranges has a second PC value for the original code differentfrom the first value. In other words, the proper value for the PC of theoriginal code depends on the region of the translated code 400 in whichan exit event occurs.

The example PC recovery table 116 includes PC values 404 that eachcorrespond to one of the address ranges 402. The example state preserver110 of FIG. 1 uses data supplied via the metadata interface 108 of theoptimizer 102 to fill in the PC values 404. That is, the exampleoptimizer 102 of FIG. 1 informs the state preserver 110 of the propercorrespondence between the addresses of the translated code 400 and theassociated proper PC value for the original code. Accordingly, should anexit event occur in the translated code 400 at an address in the [800,804] range, the PC recovery table 116 indicates that the appropriate PCvalue for the original code is 0x40490a. Other address ranges 402 andthe corresponding PC values 404 are shown in FIG. 4.

The example PC recovery table 116 also includes an EXTRACT bit 406. Theexample EXTRACT bit 406 of FIG. 4 indicates whether content of theregisters has changed such that recovery of the content is necessaryupon an exit event. That is, in some instances, execution of thetranslated code may not progress to a point at which content of theregisters is altered. If the content of the registers has not beenaltered, no need exists for recovery or re-creation of the proper stateof the registers. The example EXTRACT bit 406 provides an option toavoid unnecessary restore procedures. In the illustrated example of FIG.1, the optimizer 102 provides metadata to the state preserver 110indicative of a point in the translated code 400 at which registercontent is to be altered. The example state preserver 110 uses theprovided metadata to set the EXTRACT bit 406 in the table 116 for onesof the address ranges 402 corresponding to points in the translated codeat which register content has changed (or has likely undergone achange). In the example of FIG. 4, a value of ‘yes’ or ‘true’ indicatesthat the registers require state recovery procedures, while a value of‘no’ or ‘false’ indicates that the registers do not require staterecovery procedures. The recovery of register content is described indetail below.

The example state preserver 110 of FIG. 1 implements a JUMP_ORIGINALinstruction for use in the translated code generated by the example codeoptimizer 102. In the example of FIG. 1, the state preserver 110includes a JUMP_ORIGINAL inserter 118 to insert the instruction at apoint in the translated code. In some examples, the point at which theJUMP_ORIGINAL instruction is to be inserted is based on data provided tothe state preserver 110 via the metadata interface 108. That is, theexample code optimizer 102 of FIG. 1 can inform the state preserver 110of the point in execution of the translated code at which theJUMP_ORIGINAL instruction should be inserted. In the example translatedcode 300 of FIG. 3 and the example translated code 400 of FIG. 4, theJUMP_ORIGINAL inserter 118 inserts the JUMP_ORIGINAL instruction at theend of the translated code.

The example JUMP_ORIGINAL instruction provided by the state preserver110 obtains the appropriate PC value for the original code such thatexecution is returned to the correct address in the original code (e.g.,upon completion of the translated code). Depending on which one of thePC recovery register 114 or the PC recovery table 116 is being used totrack the proper PC value for the original code, the exampleJUMP_ORIGINAL instruction either accesses the PC recovery register 114or analyzes the PC values 404 of the PC recovery table 116. The returnedvalue of the PC for the original code is then used to jump execution tothe corresponding address of the original code. In the illustratedexamples of translated code 300 and 400 of FIGS. 3 and 4, the insertedJUMP_ORIGINAL instruction is placed at the end of the translated code.Accordingly, the proper PC value of the address in the original codeshould correspond to the next instruction of the original code aftercompletion of the example loop. In particular, the proper value of thePC for the original code is 0x40493a when the JUMP_ORIGINAL instructionis encountered in the translated code 300, 400.

In addition to the proper PC value for the original code to whichexecution is to return upon a state recovery event, the example statepreserver 110 tracks and maintains a state of the registers that shouldbe restored upon a state recovery event. To enable recovery of the stateof the registers, the example state preserver 110 includes a registerpreserver 120. The example register preserver 120 preserves states ofdifferent types of registers such as, for example, vector registers andgeneral purpose registers. In some instances, the example registerpreserver 120 preserves the state of a vector register differently thana general purpose register.

As described above, the example code optimizer 102 and the exampletranslator 104 of FIG. 1 implement a vector widening technique tooptimize original code intended for (e.g., written and/or compiled for)registers of a first size that will be executed using registers of asecond size larger than the first size. The size or length of theregisters for which the original code is intended is referred to hereinas OLEN (original length). In the illustrated examples, the OLEN of theoriginal code is a number of bits in the type of register for which theoriginal code is intended. For example, when the original code is SSE128code intended for Xmm registers, OLEN is one hundred twenty-eight (128).The size or length of the registers of the computing platform 100 thatare used to execute code is referred to herein as TLEN (target length).In the illustrated examples, the TLEN is a number of bits in the type ofregisters for which the translated code is optimized. For example, whenthe translator 104 is to translate original code into translated codefor execution in 512 bit AVX512 registers, TLEN is five hundred twelve(512). As described in detail below, OLEN and TLEN are used by theexample register preserver 120 to preserve a state of the registers.

In the illustrated example of FIG. 1, the register preserver 120includes an upper portion preserver 122 and a lower portion preserver124. Vector widening performed by the example optimizer 102 translatesthe original code such that additional bits of the larger targetregisters are utilized to, for example, widen a loop for parallelexecution of more than one loop iteration. That is, the vector wideningprovided by the example optimizer 102 may involve one or more registersincluding multiple portions each dedicated to execution of a separatethread or loop iteration. As a result, some content (e.g., data) of theregisters is replaced as the translated code is executed. However, asdescribed above, the state of the registers corresponding to theexpected state associated with the original code is to be tracked suchthat the state of the registers can be recovered (e.g., in response toan exit event and/or at boundaries of atomic regions). The example upperportion preserver 122 is configured to preserve an upper portion of thevector registers utilized by the computing platform 100 to execute thetranslated code. Further, the example lower portion preserver 124 isconfigured to preserve a lower portion of the vector registers utilizedby the computing platform 100 to execute the translated code.

The example upper portion preserver 122 of FIG. 1 includes a SAVE_UPPERinserter 126, a RESTORE_UPPER inserter 128, and a zero-bit setter 130.The example upper portion preserver 122 implements a SAVE_UPPERinstruction that is inserted into translated code to preserve an upperportion of vector registers of the computing platform 100. Inparticular, the SAVE_UPPER instruction causes data of the upper portionof the registers to be saved to memory (e.g., Random Access Memory(RAM)). In the example of FIG. 1, the upper portion preserver 122defines the portion of the registers to be saved to memory according tothe values of OLEN and TLEN. For example, the upper portion preserver122 defines the upper portion of the vector registers as a range of[TLEN-1:OLEN]. Thus, the SAVE_UPPER instruction results in bits[TLEN-1:OLEN] of the vector registers to be saved to memory. To continuethe above example, when the original code is SSE128 code intended forXmm registers and the translator 104 is to translate the original codefor execution in 512 bit AVX512 registers, the SAVE_UPPER instructionprovided by the example register preserver 120 saves the bits of theaddress range [511:128] of the vector registers to memory.

In the example of FIG. 1, the register preserver 120 cooperates with thecode optimizer 102 to determine a location in the translated code atwhich the SAVE_UPPER instruction is to be inserted. For example, themetadata interface 108 provides the SAVE_UPPER inserter 126 with anaddress or pointer to an address in the translated code corresponding toa beginning of the translated code or a beginning of an atomic region.As shown in FIGS. 3 and 4, the example SAVE_UPPER inserter 126 insertsthe SAVE_UPPER instructions into a beginning portion of the translatedcode 300, 400 such that the state of the upper portions of the registersis saved to memory before the translated code begins manipulating thecontent of the vector registers.

The example upper portion preserver 122 also implements a RESTORE_UPPERinstruction that is inserted into translated code to restore the upperportion of the vector registers. In particular, the RESTORE_UPPERinstruction causes retrieval of the register data from the memory (e.g.,as stored via the SAVE_UPPER instruction) and a restoration of the dataof the upper portions of the vector registers. As described above, theexample of FIG. 1 defines the upper portion of the vector registers as[TLEN-1:OLEN]. Thus, the RESTORE_UPPER instruction results in the datastored in memory via the SAVE_UPPER instruction to be written to the[TLEN-1:OLEN] bits of the vector registers. To continue the aboveexample, when the original code is SSE128 code intended for Xmmregisters and the translator 104 is to translate the original code forexecution in 512 bit AVX512 registers, the RESTORE_UPPER instructionwrites the data stored in memory to the address range [511:128] of thevector registers.

In the example of FIG. 1, the register preserver 120 cooperates with thecode optimizer 102 to determine a location in the translated code atwhich the RESTORE_UPPER instruction is to be inserted. For example, themetadata interface 108 provides the RESTORE_UPPER inserter 128 with anaddress or pointer to an address in the translated code corresponding toan end of the translated code or an end of an atomic region. As shown inFIGS. 3 and 4, the example RESTORE_UPPER inserter 128 inserts theRESTORE_UPPER instructions at an end portion of the translated code 300,400 such that the state of the upper portions of the registers isrestored after the translated code (or a region of the translated codecorresponding to an iteration) is complete and no longer needs access tothe vector registers.

Additionally, the example upper portion preserver 122 implements thezero-bit setter 130 to indicate instances in which the upper portion ofone or more vector registers are to be zeroed instead of restored frommemory. For example, execution of translated code may proceed to a pointat which the previous state of the vector registers (e.g., according tothe previous expected state associated with the original code) does notcorrespond to the desired recovery state. In other words, the content ofthe upper portions of the vector registers that was stored to memory viathe SAVE_UPPER instruction may no longer be the desired content for theregisters upon an exit from the translated code. In some examples, theregister preserver 120 (or some other component) may determine that thestate to be saved includes all zeroes in the upper portion(s). In suchinstances, the SAVE_UPPER instruction may not have to be executed.Instead, the zero-bit setter 130 may be informed that the registers areto be zeroed instead of being restored from memory. To avoid theunnecessary procedure of recovering the state of the upper portions insuch instances, the example zero-bit setter 130 maintains a trackingvalue, such as a bitvector, for the vector registers that can be setwhen the upper portions of the registers should be zeroed instead ofrecovered from memory. For example, the bitvector may include a bit foreach vector register and the respective bits can be set to ‘1’ or ‘0’ bythe example zero-bit setter 130. In the illustrated example, themetadata interface 108 informs the example zero-bit setter 130 when oneof the vector registers no longer needs to be restored from memory for aproper state recovery (e.g., upon an exit event from the translatedcode). In response, the zero-bit setter 130 sets the corresponding bitin the bitvector. Without information from the metadata interface 108(or any other suitable source of information) to the contrary, theexample zero-bit setter 130 keeps the bits of the bitvector at ‘0’ suchthat the upper portions of the vector registers are recovered frommemory. As described below in connection with the example state restorer112, the values of the bitvector managed by the zero-bit setter 130 arechecked when the RESTORE_UPPER instruction is encountered duringexecution of the translated code. For vector registers having a set bit(e.g., ‘1’) in the bitvector, the upper portion ([TLEN-1:OLEN]) iszeroed. For vector registers having an unset bit (e.g., ‘0’) in thebitvector, the upper portion is recovered from memory.

The example lower portion preserver 124 of FIG. 1 implements aregister-to-register bitvector setter 132 to enable preservation andrecovery (e.g., in response to an exit event in the translated code) ofthe lower portions of vector registers of the computing platform 100.The example lower portion preserver 124 generates and maintains aregister-to-register bitvector that is set by the register-to-registerbitvector setter 132 in accordance with data provided via the metadatainterface 108. As described above, the optimizer 102 and the translator104 utilize additional bits of the larger vector registers (relative tothe register size for which the original code is written and/orcompiled) via the vector widening technique. This utilization of thevector register bits may include moving the data of the lower portion ofthe vector register to a different portion of the same vector register.In other words, the vector widening implemented by the example optimizer102 may involve storing a state of the lower portion of a first vectorregister at a different location within the first vector register forpurposes of a later potential recovery. Thus, the state of the firstvector register that is to be recreated or restored upon, for example,an exit event is stored in the same first vector register via theoptimization of the original code.

When the lower portion of a vector register is to be recovered from thesame vector register, the example optimizer 102 provides information tothe lower portion preserver 124 regarding a manner in which the lowerportion data is to be recovered. In particular, for each vectorregister, the example metadata interface 108 provides a tracking valueindicative of an address range in the respective vector register atwhich the state recovery data can be found. The tracking value providedby the metadata interface 108 is used by the exampleregister-to-to-register bitvector setter 132 to set the correspondingbit(s) of the register-to-register bitvector. In the illustratedexample, the register preserver 120 defines a value referred to hereinas a WidenFactor. The WidenFactor is equal to TLEN/OLEN. To continue theabove example, the WidenFactor of the illustrated example is 512/128,which evaluates to four (4). The tracking value provided by theoptimizer 102 for each vector register has a length oflog_(—)2(WidenFactor). The register-to-register bitvector includes anentry for each vector register. Therefore, the register-to-registerbitvector has a length of log_(—)2(WidenFactor)*(the number of vectorregisters) bits. To continue the above example, with the assumption thatthe number of vector registers is equal to 20, the register-to-registerbitvector is (2)*(20), which evaluates to forty (40) bits.

For each of the vector registers, the example register-to-registerbitvector setter 132 uses the tracking value provided by the optimizer102 to set the respective bit(s) of the register-to-register bitvector.In the illustrated example, when the tracking value for each vectorregister has a length of two (2) bits (e.g., when the WidenFactor isfour (4)), a value of ‘00’ corresponding to an instance in which thedata does not need to be recovered from a region to which the data wasrelocated. For example, the tracking value being ‘00’ may correspond toan instance in which the lower portion of the vector register was notrelocated inside the vector register as part of the optimization processor otherwise does not require a recovery process (e.g., when thetranslation code has been executed to a point at which the previousstate of the register is no longer valid for a state recovery process).On the other hand, the tracking value may be set to ‘01’ ‘10’ or ‘11.’Each of the possible values of the tracking value provided via themetadata interface 108 corresponds to a region in the correspondingvector register at which the data of a lower portion of the same vectorregister to be restored can be retrieved.

In particular, the tracking value is set according to an equation to beutilized by the example state restorer 112 when recovering a state ofthe vector registers. In the illustrated example, where the trackingvalue is represented by ‘d,’ the location within a vector register fromwhich the state recovery data is to be retrieved is[OLEN*(d)−1:OLEN*(d−1)]. Further, the lower portion of the vectorregister is defined as [OLEN−1:0]. Accordingly, upon a state recoverytrigger (e.g., an exit event in the translated code), when the lowerportion of a vector register is to be recovered from a location withinitself, the bits at [[OLEN*(d)−1:OLEN*(d−1)] are copied to [OLEN−1:0] ofthe vector register. In some examples, one or more additional bits ofthe vector register are zeroed to comply with one or more requirementsof the register format and/or protocol.

As an example implementation of the register-to-register bitvector,assume that the translator 104 has translated scalar 64 bit doubleprecision floating point original code for a 512 bit AVX registersystem. Thus, OLEN is sixty-four (64), TLEN is five hundred twelve(512), the WidenFactor is eight (8), and each vector register has three(3) bits in the register-to-register bitvector. When the metadatainterface 108 provides a tracking value of two (2) for a particularvector register, the example register-to-register bitvector setter 132sets the three bits of the bitvector corresponding to the particularvector register to ‘010.’ When the state restorer 112 checks theappropriate portion of the register-to-register bitvector and determinesthat the value is ‘010,’ the value of two (2) is inserted into the aboveequation to identify the proper manner of restoring the lower portion ofthe particular vector register. When ‘d’ equal two (2) in the aboveequation, the state restorer 112 determines that the bits at [127:64] ofthe vector register are to be copied to [63:0] to restore the lowerportion of the vector register.

The example lower portion preserver 124 also generates and maintains amemory-register bitvector that is set by a memory-to-register bitvectorsetter 134. The example memory-to-register bitvector maintained by theexample lower portion preserver 124 indicates whether any of theregisters have lower portion data that is to be restored from memory (asopposed to another location of the same register to which the data wasrelocated per the optimization). For example, the lower portion of someof the vector registers may be stored to memory as part of theoptimization. Additionally, in the illustrated example of FIG. 1, entirecontent of the general purpose registers are copied to memory beforeexecution of the translated code. For each of the registers having datato be restored from memory, the example memory-to-register bitvectorsetter 134 sets a corresponding entry of the memory-to-registerbitvector. Thus, when an entry in the memory-to-register bitvector for aparticular vector register is set (e.g., to ‘1’), the example staterestorer 112 is informed that the lower portion of the vector registeris to be recovered from memory upon a state recovery trigger (e.g., anexit from the translated code). Further, when an entry in thememory-to-register bitvector for a particular general purpose registeris set (e.g., to ‘1’), the example state restorer 112 is informed thatthe entire content of the general purpose register is to be recoveredfrom memory. On other hand, when the entry in the memory-to-registerbitvector for the general purpose register is not set (e.g., is ‘0’),the example state restorer 112 is informed that the general purposeregister need not be recovered (e.g., when the stored state of thegeneral purpose register is no longer valid for a state recoveryprocess). The example state restorer 112 recovers the lower portions ofthe vector registers and/or the entire general purpose registersaccording to the memory-to-register bitvector by copying the appropriatevalues from memory to the lower OLEN bits of the register (bit range[OLEN−1:0]).

While an example manner of implementing the platform 100 has beenillustrated in FIG. 1, one or more of the elements, processes and/ordevices illustrated in FIG. 1 may be combined, divided, re-arranged,omitted, eliminated and/or implemented in any other way. Further, theexample code optimizer 102, the example translator 104, the examplestate recovery mechanism 106, the example metadata interface 108, theexample state preserver 110, the example state restorer 112, the examplePC recovery register 114, the example PC recovery table 116, the exampleJUMP_ORIGINAL inserter 118, the example register preserver 120, theexample upper portion preserver 122, the example lower portion preserver124, the example SAVE_UPPER inserter 126, the example RESTORE_UPPERinserter 128, the example zero-bit setter 130, the exampleregister-to-register bitvector setter 132, the examplememory-to-register bitvector setter 134 and/or, more generally, theexample platform 100 of FIG. 1 may be implemented by hardware, software,firmware and/or any combination of hardware, software and/or firmware.Thus, for example, any of the example code optimizer 102, the exampletranslator 104, the example state recovery mechanism 106, the examplemetadata interface 108, the example state preserver 110, the examplestate restorer 112, the example PC recovery register 114, the example PCrecovery table 116, the example JUMP_ORIGINAL inserter 118, the exampleregister preserver 120, the example upper portion preserver 122, theexample lower portion preserver 124, the example SAVE_UPPER inserter126, the example RESTORE_UPPER inserter 128, the example zero-bit setter130, the example register-to-register bitvector setter 132, the examplememory-to-register bitvector setter 134 and/or, more generally, theexample platform 100 of FIG. 1 could be implemented by one or morecircuit(s), programmable processor(s), application specific integratedcircuit(s) (ASIC(s)), programmable logic device(s) (PLD(s)) and/or fieldprogrammable logic device(s) (FPLD(s)), etc. When any of the appendedsystem or apparatus claims of this patent are read to cover a purelysoftware and/or firmware implementation, at least one of the examplecode optimizer 102, the example translator 104, the example staterecovery mechanism 106, the example metadata interface 108, the examplestate preserver 110, the example state restorer 112, the example PCrecovery register 114, the example PC recovery table 116, the exampleJUMP_ORIGINAL inserter 118, the example register preserver 120, theexample upper portion preserver 122, the example lower portion preserver124, the example SAVE_UPPER inserter 126, the example RESTORE_UPPERinserter 128, the example zero-bit setter 130, the exampleregister-to-register bitvector setter 132, the examplememory-to-register bitvector setter 134 and/or, more generally, theexample platform 100 of FIG. 1 are hereby expressly defined to include atangible computer readable storage medium such as a memory, DVD, CD,Blu-ray, etc. storing the software and/or firmware. Further still, theexample platform 100 of FIG. 1 may include one or more elements,processes and/or devices in addition to, or instead of, thoseillustrated in FIG. 1, and/or may include more than one of any or all ofthe illustrated elements, processes and devices.

The example state recovery mechanism 106 of FIG. 1 can be implementedvia a micro code sequence that is inserted into program execution (e.g.,as a micro-code assist). Additionally or alternatively, the examplestate recovery mechanism 106 can be an explicit recovery handler thatinvokes a runtime code of the computing platform 100 to perform thefunctionality disclosed herein.

FIGS. 5-7 are flowcharts representative of example machine readableinstructions for implementing the example platform 100 of FIG. 1. In theexample flowcharts of FIGS. 5-7, the machine readable instructionscomprise program(s) for execution by a processor such as the processor812 shown in the example computer 800 discussed below in connection withFIG. 8. The program(s) may be embodied in software stored on a tangiblecomputer readable medium such as a CD-ROM, a floppy disk, a hard drive,a digital versatile disk (DVD), a Blu-ray disk, or a memory associatedwith the processor 812, but the entire program and/or parts thereofcould alternatively be executed by a device other than the processor 812and/or embodied in firmware or dedicated hardware. Further, although theexample program(s) is described with reference to the flowchartsillustrated in FIGS. 5-7, many other methods of implementing the exampleplatform 100 may alternatively be used. For example, the order ofexecution of the blocks may be changed, and/or some of the blocksdescribed may be changed, eliminated, or combined.

As mentioned above, the example processes of FIGS. 5-7 may beimplemented using coded instructions (e.g., computer readableinstructions) stored on a tangible computer readable medium such as ahard disk drive, a flash memory, a read-only memory (ROM), a compactdisk (CD), a digital versatile disk (DVD), a cache, a random-accessmemory (RAM) and/or any other storage media in which information isstored for any duration (e.g., for extended time periods, permanently,brief instances, for temporarily buffering, and/or for caching of theinformation). As used herein, the term tangible computer readable mediumis expressly defined to include any type of computer readable storageand to exclude propagating signals. Additionally or alternatively, theexample processes of FIGS. 5-7 may be implemented using codedinstructions (e.g., computer readable instructions) stored on anon-transitory computer readable medium such as a hard disk drive, aflash memory, a read-only memory, a compact disk, a digital versatiledisk, a cache, a random-access memory and/or any other storage media inwhich information is stored for any duration (e.g., for extended timeperiods, permanently, brief instances, for temporarily buffering, and/orfor caching of the information). As used herein, the term non-transitorycomputer readable medium is expressly defined to include any type ofcomputer readable medium and to exclude propagating signals. As usedherein, when the phrase “at least” is used as the transition term in apreamble of a claim, it is open-ended in the same manner as the term“comprising” is open ended. Thus, a claim using “at least” as thetransition term in its preamble may include elements in addition tothose expressly recited in the claim.

FIG. 5 begins with an indication that original code has been optimizedby the example optimizer 102 of FIG. 1 (block 500). For example, theindication that original code has been optimized in FIG. 5 correspondsto an instance of the translator 104 of the optimizer 102 havingoptimized the SAXPY loop code 200 of FIG. 2 according to one or morevector widening techniques. As described above, such an optimizationincludes, for example, utilizing additional bits in registers of theplatform 100 that are larger than the registers for which the originalcode 200 is written and/or compiled.

The example state recovery mechanism 106 determines whether the statepreserver 110 is configured to utilize the PC recovery register 114 orthe PC recovery table 116 to track the proper value for the PC of theoriginal code for a state recovery process (block 502). As describedabove, the proper value of the PC of the original code is tracked suchthat execution can resume from the appropriate address according to theoriginal code when, for example, an exit event occurs in connection withthe translated code. When the example state preserver 110 is configuredto utilize the PC recovery table 116 (block 502), the example statepreserver 110 communicates with the optimizer 102 via the metadatainterface 108 to generate the example PC recovery table 116 according tothe manner that the original code has been translated (block 504). Inthe illustrated example, the information provided to the state preserver110 by the optimizer 102 includes values of the PC for the original codethat should be used for a state recovery process at different addressranges in the translated code. As shown in FIG. 4, the example PCrecovery table 116 includes the provided PC values 404 and thecorresponding address ranges 402 of the translated code. As describedabove, the address ranges 402 of the translated code correspond to, forexample, atomic regions and/or the boundaries that define atomic regionsof the translated code. When the PC recovery table 116 has beengenerated in the example of FIG. 5, control then proceeds to block 510.

Referring to block 502, when the state preserver 110 is configured toutilize the PC recovery register 114, the example state preserver 110communicates with the optimizer 102 via the metadata interface 108 toobtain data to be loaded into the PC recovery register 114. The data tobe loaded into the PC recovery register 114 is indicative of a PC valuefor the original code corresponding to a current point in execution ofthe translated code. The example state preserver 110 inserts loadinstructions into the translated code according to the informationreceived from the optimizer 102 such that the data stored in the PCrecovery register 114 at different point throughout execution of thetranslated code includes the proper value of the PC for the originalcode that should be used for a state recovery process at the respectivepoints in the translated code (block 506).

To preserve the upper portions of the vector registers of the computingplatform in a certain state, the example SAVE_UPPER inserter 126 insertsone or more SAVE_UPPER instructions into the translated code (block508). When executed, the SAVE_UPPER instruction copies bits in theaddress range [TLEN-1:OLEN] of the vector registers to memory. Further,the example RESTORE_UPPER inserter 128 inserts one more RESTORE_UPPERinstructions into the translated code that each correspond to aSAVE_UPPER instruction (block 510). When executed, the RESTORE_UPPERinstruction restores the bits in the address range [TLEN-1:OLEN] of thevector registers from memory. The example of FIG. 5 then ends (block512).

FIG. 6 begins with an initiation of execution of the translated code(block 600). As described above, the translator 104 of the optimizer 102has translated the original code into optimized code. The exampleoptimizer 102 of FIG. 1 provides information to the state recoverymechanism 106 (e.g., via the metadata interface 108) regarding theoptimization of the original code. The example lower portion preserver124 of FIG. 1 uses the metadata provided by the optimizer 102 to thememory-to-register bitvector via the memory-to-register bitvector setter134 (block 602). The bit(s) in the bitvector associated with register(s)having content stored in memory for preservation (e.g., such that thecontent is recovered from memory in response to, for example, an exitevent in the translated code) are set by the memory-to-registerbitvector setter 134. Accordingly, the memory-to-register bitvectormaintained by the lower portion preserver 124 indicates which of theregisters, such as the general purpose registers, are to be recovered bycopying data from memory.

The example lower portion preserver 124 calculates the WidenFactor forthe optimization implemented by the example optimizer 102 (block 604).In the illustrated example, the WidenFactor is TLEN/OLEN. Further, forthe vector registers having a state of the corresponding lower portionstored in the same vector register for purposes of a state recovery, theexample register-to-register bitvector setter 132 configures the bit(s)in the register-to-register bitvector maintained by the example lowerportion preserver 124 (block 606). As described above, the exampleregister-to-register bitvector setter 132 uses a tracking value providedby the optimizer 102 to set the appropriate bit(s) of theregister-to-register bitvector. The tracking value provided by theoptimizer 102 is indicative of a location in a vector register at whichthe data of the lower portion to be restored has been relocated. If anupdated tracking value is provided by the optimizer 102 during executionof the translated code (block 608), the example register-to-registerbitvector setter 132 adjusts the register-to-register bitvectoraccordingly (block 610). When the execution of the translated code isnot complete (block 612), control returns to block 608. Otherwise, theexample of FIG. 6 ends (block 614).

FIG. 7 begins with a state recovery process being triggered (block 700).As described above, the state recovery process can be triggered by, forexample, an exit event (e.g., an exception, an interrupt, a trap, etc.)occurring in the translated code and/or a completion of the translatedcode and/or completion of a portion (e.g., an atomic region) of thetranslated code. When recovering a state of the computing platform 100,the example state recovery mechanism 106 of FIG. 1 is to restore orprovide a proper value of the PC for the original code such that theproper point of execution in the original code is identified for thestate recovery. The example state recovery mechanism 106 implements thePC recovery register 114 and the PC recovery table 116 that each may beused to track the proper value of the PC for the original code. If thePC recovery table 116 is currently being used to track the PC value(block 702), the example state restorer 112 determines whether theextract bit is set for the appropriate entry in the PC recovery table116 (block 704). In particular, the address in the translated codecorresponding to the triggered state recovery at block 700 has anassociated EXTRACT bit 406 in the PC recovery table 116. If the EXTRACTbit 406 is set (block 704), then control proceeds to block 706.Otherwise, if the EXTRACT bit is not set (block 704), control proceedsto block 710.

Thus, if the EXTRACT bit 406 is set in the entry of the PC recoverytable 116 (block 704) or if the state preserver 110 is utilizing the PCrecovery register 114 rather than the PC recovery table 116 (block 702),the example state restorer 112 restores the lower portions of the vectorregisters based on the register-to-register bitvector (block 706). Asdescribed above, the restoration or recreation of the lower portions ofthe vector registers uses the respective bit(s) of theregister-to-register bitvector to locate the data of the recovery statewith the same vector registers. In the illustrated example, the staterestorer 112 determines the location within each vector register fromwhich the state recovery data is to be retrieved is as[OLEN*(d)−1:OLEN*(d−1)], where the value of the respective bit(s) of thebitvector is represented by ‘d.’ Further, the lower portion of thevector register to be restored is defined as [OLEN−1:0].

The example state restorer 112 also restores data to registers, such asthe general purposes registers and/or vector registers having datastored in memory, according to the memory-to-register bitvector (block708). After the data of the lower portions of the vector registers hasbeen restored, the example state restorer 112 executes the RESTORE_UPPERinstruction, which checks the value of the zero bitvector and restoresthe upper portions of the vector registers in accordance with the zerobitvector (block 710). As described above, a bit of the zero bitvectorbeing set results in the corresponding upper portion being zeroed forthe restoration thereof. Otherwise, when the bit is not set, the data ofthe upper portions corresponding to the state being recovered is copiedinto the vector registers from memory, where the SAVE_UPPER instructionspreviously stored the data.

The tracked value of the PC for the original code is recovered from thePC recovery register 114 or the PC recovery table depending on which ofthe recovery mechanisms is being used by the state preserver 110 for thecurrent instance of the translated code (block 712). The example staterestorer 112 executes the JUMP_ORIGINAL instruction using the recoveredPC value such that execution jumps to the corresponding address in theoriginal code (block 714). The example of FIG. 7 then ends (block 716).

FIG. 8 is a block diagram of a processor platform 800 capable ofexecuting the instructions of FIGS. 5-7 to implement the exampleplatform 100 of FIG. 1. The processor platform 800 can be, for example,a server, a personal computer, an Internet appliance, a DVD player, a CDplayer, a Blu-ray player, a gaming console, a personal video recorder, asmart phone, a tablet, a printer, or any other type of computing device.

The processor platform 800 of the instant example includes a processor812. For example, the processor 812 can be implemented by one or moremicroprocessors or controllers from any desired family or manufacturer.

The processor 812 includes a local memory 813 (e.g., a cache) and is incommunication with a main memory including a volatile memory 814 and anon-volatile memory 816 via a bus 818. The volatile memory 814 may beimplemented by Synchronous Dynamic Random Access Memory (SDRAM), DynamicRandom Access Memory (DRAM), RAMBUS Dynamic Random Access Memory (RDRAM)and/or any other type of random access memory device. The non-volatilememory 816 may be implemented by flash memory and/or any other desiredtype of memory device. Access to the main memory 814, 816 is controlledby a memory controller.

The processor platform 800 also includes an interface circuit 820. Theinterface circuit 820 may be implemented by any type of interfacestandard, such as an Ethernet interface, a universal serial bus (USB),and/or a PCI express interface.

One or more input devices 822 are connected to the interface circuit820. The input device(s) 822 permit a user to enter data and commandsinto the processor 812. The input device(s) can be implemented by, forexample, a keyboard, a mouse, a touchscreen, a track-pad, a trackball,isopoint and/or a voice recognition system.

One or more output devices 824 are also connected to the interfacecircuit 820. The output devices 824 can be implemented, for example, bydisplay devices (e.g., a liquid crystal display, a cathode ray tubedisplay (CRT), a printer and/or speakers). The interface circuit 820,thus, typically includes a graphics driver card.

The interface circuit 820 also includes a communication device such as amodem or network interface card to facilitate exchange of data withexternal computers via a network 826 (e.g., an Ethernet connection, adigital subscriber line (DSL), a telephone line, coaxial cable, acellular telephone system, etc.).

The processor platform 800 also includes one or more mass storagedevices 828 for storing software and data. Examples of such mass storagedevices 828 include floppy disk drives, hard drive disks, compact diskdrives and digital versatile disk (DVD) drives.

The coded instructions 832 of FIG. 5-7 may be stored in the mass storagedevice 828, in the volatile memory 814, in the non-volatile memory 816,and/or on a removable storage medium such as a CD or DVD.

Example methods include inserting a first instruction into optimizedcode to cause a first portion of a register in a first state to be savedto memory before execution of a region of the optimized code; andmaintaining a value indicative of a manner in which a second portion ofthe register in the first state is to be restored in connection with astate recovery from the optimized code.

Some example methods further include inserting a second instruction intothe optimized code to cause the first portion of the register in thefirst state to be restored from the memory after execution of the regionof the optimized code.

Some example methods further include defining the first portionaccording to a relationship between a first size of the register and asecond size of a second register associated with original code on whichthe optimized code is based.

In some example methods, the original code is intended for execution inthe second register.

In some example methods, the value is to indicate the manner in whichthe second portion is to be restored by providing a location within theregister at which data of the second portion is relocated as part of anoptimization of original code.

Some example methods further include maintaining an address of originalcode on which the optimized code is based, the address corresponding toa point in execution of the original code for a state recovery to thefirst state.

In some example methods, the maintaining of the address includesinserting load instructions into the optimized code to cause the addressto be stored in a dedicated register.

Some example methods further include storing the address in a tablehaving an entry corresponding to the address that includes an addressrange of the translated code.

Example tangible machine readable storage media include instructionsthat, when executed, cause a machine to at least: insert a firstinstruction into optimized code to cause a first portion of a registerin a first state to be saved to memory before execution of a region ofthe optimized code; and maintain a value indicative of a manner in whicha second portion of the register in the first state is to be restored inconnection with a state recovery from the optimized code.

In some examples, the instructions, when executed, cause the machine toinsert a second instruction into the optimized code to cause the firstportion of the register in the first state to be restored from thememory after execution of the region of the optimized code.

In some examples, the instructions, when executed, cause the machine todefine the first portion according to a relationship between a firstsize of the register and a second size of a second register associatedwith original code on which the optimized code is based.

In some examples, the original code is intended for execution in thesecond register.

In some examples, the value is to indicate the manner in which thesecond portion is to be restored by providing a location within theregister at which data of the second portion is relocated as part of anoptimization of original code.

In some examples, the instructions cause the machine to maintain anaddress of original code on which the optimized code is based, theaddress corresponding to a point in execution of the original code for astate recovery to the first state.

In some examples, the instructions cause the machine to maintain theaddress by inserting load instructions into the optimized code to causethe address to be stored in a dedicated register.

In some examples, the instructions cause the machine to store theaddress in a table having an entry corresponding to the address thatincludes an address range of the translated code.

Example apparatus include a register having a first size; a translatorto optimize original code into translated code, the original code beingintended for execution in registers of a second size different than thefirst size; and a state preserver to: save data of an upper portion ofthe register in a first state to memory before execution of a region ofthe translated code; and maintain a value indicative of a location inthe register at which data of a lower portion of the register in thefirst state is relocated in connection with the optimization of theoriginal code.

Some example apparatus further include a recovery table to store anaddress range of the translated code and a corresponding address of theoriginal code to which execution is to return in response to a staterecovery being triggered in connection with the address range of thetranslated code.

In some examples, the recovery table includes a bit indicative ofwhether data of the register in the first state is to be restored inresponse to the state recovery being triggered.

In some examples, the state preserver is to maintain the value based onmetadata provided by the translator.

Some example apparatus further include a restorer to restore the data ofthe upper portion of the register in the first state from the memory inresponse to a state recovery being triggered.

Some example apparatus further include a restorer to restore data of thelower portion of the register in the first state from the location ofthe register according to the value.

Although certain example apparatus, methods, and articles of manufacturehave been disclosed herein, the scope of coverage of this patent is notlimited thereto. On the contrary, this patent covers all apparatus,methods, and articles of manufacture fairly falling within the scope ofthe claims of this patent.

What is claimed is:
 1. A method, comprising: inserting a first instruction into optimized code, the first instruction to cause first data of a first portion of a register to be saved to memory before execution of a region of the optimized code; and maintaining a value indicative of a location within the register to which second data of a second portion of the register is relocated, the second data to be restored, using the value, to the second portion of the register from the location within the register in connection with a state recovery, the state recovery to restore the register to a state with the first data in the first portion of the register and the second data in the second portion of the register, the first portion of the register being different than the second portion of the register.
 2. A method as defined in claim 1, further comprising inserting a second instruction into the optimized code, the second instruction to cause the first data of the first portion of the register to be restored from the memory as part of the state recovery.
 3. A method as defined in claim 1, wherein the register is a first register, and further comprising defining the first portion according to a relationship between a first size of the first register and a second size of a second register.
 4. A method as defined in claim 3, wherein the optimized code is based on original code structured for execution via the second register of the second size.
 5. A method as defined in claim 1, wherein the second data of the second portion of the register is relocated as part of an optimization of original code.
 6. A method as defined in claim 1, further comprising maintaining an address of original code on which the optimized code is based, the address corresponding to a point in execution of the original code, the point to be used in the state recovery.
 7. A method as defined in claim 6, wherein the maintaining of the address comprises inserting a load instruction into the optimized code to cause the address to be stored in a dedicated register.
 8. A method as defined in claim 6, further comprising storing the address in a table having an entry corresponding to the address that includes an address range of the original code.
 9. A tangible machine readable storage medium comprising instructions that, when executed, cause a machine to at least: insert a first instruction into optimized code, the first instruction to cause first data of a first portion of a register to be saved to memory before execution of a region of the optimized code; and maintain a value indicative of a location within the register to which second data of a second portion of the register is relocated, the second data to be restored, using the value, to the second portion of the register from the location within the register in connection with a state recovery, the state recovery to restore the first data to the first portion of the register and the second data to the second portion of the register, the first portion of the register being different than the second portion of the register.
 10. A tangible machine readable storage medium as defined in claim 9, wherein the instructions, when executed, cause the machine to insert a second instruction into the optimized code, the second instruction to cause the first data of the first portion of the register to be restored from the memory as part of the state recovery.
 11. A tangible machine readable storage medium as defined in claim 9, wherein the register is a first register, and the instructions, when executed, cause the machine to define the first portion according to a relationship between a first size of the first register and a second size of a second register.
 12. A tangible machine readable storage medium as defined in claim 11, wherein the optimized code is based on original code structured for execution via the second register of the second size.
 13. A tangible machine readable storage medium as defined in claim 9, wherein the second data of the second portion of the register is relocated as part of an optimization of original code.
 14. A tangible machine readable storage medium as defined in claim 9, wherein the instructions, when executed, cause the machine to maintain an address of original code on which the optimized code is based, the address corresponding to a point in execution of the original code, the point to be used in the state recovery.
 15. A tangible machine readable storage medium as defined in claim 14, wherein the instructions, when executed, cause the machine to maintain the address by inserting a load instruction into the optimized code to cause the address to be stored in a dedicated register.
 16. A tangible machine readable storage medium as defined in claim 14, wherein the instructions, when executed, cause the machine to store the address in a table having an entry corresponding to the address that includes an address range of the original code.
 17. An apparatus, comprising: a register having a first size; a translator to translate original code into translated code, the original code structured for execution via registers of a second size different than the first size; and a state preserver to: save data of an upper portion of the register to memory before execution of a region of the translated code; and maintain a value indicative of a location in the register at which data of a lower portion of the register is relocated in connection with translation of the original code.
 18. An apparatus as defined in claim 17, further comprising a recovery table to store an address range of the translated code and a corresponding address of the original code to which execution is to return in response to a state recovery being triggered in connection with the address range of the translated code.
 19. An apparatus as defined in claim 18, wherein the recovery table comprises a bit indicative of whether data of the register is to be restored in response to the state recovery being triggered.
 20. An apparatus as defined in claim 17, wherein the state preserver is to maintain the value based on metadata provided by the translator.
 21. An apparatus as defined in claim 17, further comprising a restorer to restore the data of the upper portion of the register from the memory in response to a state recovery being triggered.
 22. An apparatus as defined in claim 17, further comprising a restorer to restore data of the lower portion of the register from the location of the register according to the value. 